The proposed experiments will test a three lectin model of amebic encystations and excystation. A constitutive plasma membrane Gal/GalNAc lectin bound sugars in a unique, abundant, encystations-specific glycoprotein (Jacob), which was first identified here. Jacob was named for a ladder-like series of five Cys-rich, chitin-binding domains (CBD) which resemble CBD of chitinases and peritophin-44, an insect gut wall protein. Anti-Jacob antibodies bound to cyst isolated from patient stools. Galactose inhibited cyst wall formation by blocking binding of Jacob and subsequently chitin to the amebic surface. An encystations-specific chitinase had a Cys-richlectin domain, which resembles those of wheat germ agglutinin and plant chitinases. GlucNAc inhibited binding of Jacob and chitinase to chitin in SDS-treated cyst walls.